Details

Autor(en) / Beteiligte

• Jury, A.
• Balandraud, X.
• Heller, L.

Titel

Thermal Conductivity and Specific Heat Capacity of Austenite and Stress-Induced Martensite in Superelastic NiTi at Ambient Temperature

Ist Teil von

• International journal of thermophysics, 2023-11, Vol.44 (11), Article 162

Ort / Verlag

New York: Springer US

Erscheinungsjahr

2023

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Infrared thermography (IRT) and heat source reconstruction (HSR) were used in the study to measure two thermophysical properties of superelastic nickel-titanium (NiTi) shape memory alloy (SMA) wires, namely thermal conductivity and specific heat capacity. Since the values are potentially phase dependent, the identification was carried out at ambient temperature with and without mechanical loading, i.e., in the stress-induced martensite state and in the austenite state, respectively. A uniaxial testing machine was used to apply constant deformation while allowing temperature measurements by IRT during Joule heating and natural return the thermal equilibrium. The data processing by HSR, including preliminary filtering operations, was preliminarily evaluated from temperatures provided by a model (with added noise). It gave an error of ± 0.5% for the thermal conductivity and ± 1% for the specific heat capacity. The experimental analysis showed that the thermal conductivity of stress-induced martensite is 26% higher than that of austenite at the same temperature (here the ambient temperature). Regarding the specific heat capacity, that of stress-induced martensite is 4.7% lower than that of austenite. Explanations for these differences were proposed from solid-state physics theory. The measured values were also compared to data collected in the literature (obtained at zero stress at different temperatures).